Recovering solvent from solvent diluted tailings has various challenges. Solvent diluted tailings are often derived from extraction operations that use solvent to aid in the separation of the valuable product, such as bitumen, from other components of an ore.
In bitumen extraction operations, various stages of the bitumen extraction can include the addition of hydrocarbon-based solvent to a bitumen-containing mixture in order to produce solvent diluted bitumen and solvent diluted tailings. For instance, oil sands ore can be subjected to primary extraction where the oil sands ore is mixed with water and the resulting slurry is supplied to a primary extraction system that produces tailings and bitumen froth. The bitumen froth can then be subjected to secondary extraction that involves the addition of solvent to the bitumen froth. Secondary extraction can also be referred to as “froth treatment” and may include the addition of paraffinic solvent, naphthenic solvent (often referred to as “diluent”), or other hydrocarbon-based solvents. The bitumen froth includes water and mineral solids that should be removed in order to produce a bitumen stream that can be stored and pipelined. Such solvent-assisted extraction can be carried out in a froth separation unit (FSU) and enables water and mineral solids to be substantially removed from the bitumen froth. The FSU thus produces solvent diluted bitumen and solvent diluted tailings.
Solvent diluted tailings, which may be produced as an underflow stream of the FSU, can include water, mineral solids, residual bitumen, as well as precipitated asphaltene-containing flocs or aggregates when certain precipitation solvents (e.g., paraffinic solvents) are used. Recovering the solvent typically involves supplying the solvent diluted tailings to one or more separation vessels, which are part of a tailings solvent recovery unit (TSRU) and are operated so that the solvent vaporizes and is recovered as an overhead stream while the other less volatile components including water and mineral solids are recovered as a solvent depleted underflow stream.
However, introducing the solvent diluted tailings into the separation vessels of the TSRU can be challenging. For instance, the solvent diluted tailings include solid mineral particles that can increase the wear on equipment particularly in the context of vapour-slurry separation. Premature flashing of the solvent in the feed stream prior to introduction into the chamber of the separation vessel accelerate the solids and cause significant erosion of the inlet equipment. Introducing multiphase streams, such as solvent diluted tailings, for separation of a volatile component from a liquid or slurry component can also be challenging due to complex fluid dynamics and mass transfer phenomena in the inlet equipment and the separation vessels.